As a general rule, units of this type (radar or optoelectronic systems) are coupled to a surveillance radar whose function is to acquire the target or targets and then to transfer the designation data from a target to a tracking radar. When the surveillance unit is a radar system, the target-designation data delivered by this system are the azimuth angle and the target distance or range. When the surveillance unit consists of passive optoelectronic means such as a television or infrared camera, the target-designation data are the azimuth angle and the elevation angle. In the ensuing description of my present invention, consideration will be given only to surveillance radar systems which give the target distance and are equipped with antennas of the mobile directional type.
The tracking unit can also be an optoelectronic device of either the passive or the active type (which is the case of a laser) or alternatively a radar system.
With a passive unit it is not possible to obtain an accurate measurement of the distance or range of the target, which is a major drawback. In the case of an active tracking system, this system is liable to be jammed, in particular by a detection jammer of the telemetry-thief type. It becomes impossible in such a case to determine the target distance with accuracy and therefore to determine the course or variations in trajectory of the target.